When it comes to tree health, variety is the best defense
April 11, 2011
Spring is just around the corner and if you’re thinking about what kind of tree to plant when the ground finally thaws, the old axiom of “variety is the spice of life” is worth keeping in mind.
In general, the more diverse a landscape, the healthier it is. This is especially true for the landscape that surrounds our daily lives, that collection of trees and other plants referred to commonly as the community forest. Time and again, insects or diseases have wiped out important individual species within this forest. None has been more devastating than Dutch elm disease, which decimated the American elm in the 1960s and ’70s. Now a foreign invader called the emerald ash borer looms as a very real threat to one of our most commonly planted trees – the green ash and its native cousins.
So let’s think diversity. Even in a relatively treeless place like Nebraska, there are dozens of underused tree species, both native and introduced, that have proven to be adaptable and worthy of more usage. Although many non-native trees are worthy of planting within towns, native trees offer a very important benefit in that they typically support a much wider web of life. Some native oak species support more than two dozen species of birds and hundreds of species of important insects.
A few tree species deserving greater use are described below, but there are many other species and varieties also worthy of consideration. For more ideas, check with your local nursery or go to ReTreeNebraska.unl.edu.
• Bur Oak (and its cousins): Bur oak is native across much of the state and should definitely be planted more in urban areas. It is extremely adaptable to a wide variety of conditions and is amazingly drought tolerant. It is also one of the most important trees for supporting wildlife including dozens of bird species and hundreds of important insects. Its cousins the red, chinkapin, black, white, shingle and other oaks also should be considered.
• Sugar Maple: In the upper Midwest and New England, sugar maple is a common forest and landscape tree. Unfortunately, it is uncommon in Nebraska. That’s too bad since its rounded shape, clean foliage, shade-tolerance, drought-tolerance and great fall color make it such a welcome addition to just about any landscape. Many sugar maples dot the landscapes of eastern Nebraska towns so the species is proven. Ultimate size range is 40-60 feet tall by 35-50 feet wide.
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• Miyabe Maple: Miyabe maple (pronounced my-ah-bee) is a relatively new species to the North American landscape, having been introduced here from Asia. It has proven itself adaptable and drought-tolerant in plantings throughout the Midwest for the last several decades. Its shape and foliage are similar to that of sugar maple, with a smaller leaf and a slightly smaller habit, growing 30-40 feet tall and up to 30 feet wide.
• Catalpa: With its large, heart-shaped leaves, showy white flowers and long, cigar-shaped seed pods, catalpa is most definitely an oddball in the landscape. This Midwest native has proven to be very adaptable and drought-tolerant and is a favorite resting site for many important birds, including some hawks and owls. The tree typically grows upright, becoming taller than wide over time, and reaching 60 feet tall or more.
• Tuliptree (tulip poplar): Though not native to Nebraska, this southeastern U.S. species has proven adaptable to the eastern part of the state. Its glossy, distinctive leaves are unlike anything else in the landscape. It is best known for its upward-reaching, tulip-like flowers that appear at the branch tips after the first leaves unfurl. Its upright habit and rustling leaves somewhat mimic cottonwood, causing many to think it is a variety of poplar, though it is not. Tuliptree can grow 50-70 feet tall and 40-50 feet wide.